Methods of making fabrics from synthetic tapes

ABSTRACT

A supply roll of longitudinally oriented synthetic sheet is provided having alternating relatively thick longitudinal ribs and relatively thin longitudinal webs. The sheet is advanced, and selected webs are torn to separate the sheet into a plurality of tapes of a desired width. The tapes are then fed directly in line into a loom or knitting machine and woven or knitted into a fabric.

United States Patent 1191 1111 3,918,135

Kim Nov. 11, 1975 [5 METHODS OF MAKING FABRICS FROM 3.626.989 12/1971 Held 139/11 SYNTHETIC TAPES 3.645.299 2/1972 Eichler 139/11 3,7l2.344 l/l973 Kovzicec l39/ll Inventor: Charles W-Kim,Wilm1I1gtOn,Del- 3.732.708 5/1973 Troy 28/1 cs 3.769.815 11/1973 Ploch et :1]... 28/DIG. 1 [73] Assgnee' gg Incorporated wllmmgton- 1127.727 8/1973 Kim et al. 28/DIG, 1 [22] Filed: Sept. 17, 1973 FOREIGN PATENTS OR APPLICATIONS 980.288 H1965 United Kingdom 139/420 R pp 397,489 1,035,227 7/1966 United Kingdom 139/11 1267031 3/1972 United Kingdom 52 us. 01. 28/72 cs; 28/1 cs; 66/125 R; 4845213 1973 139/11;139/420 R; 264/103 J K 51 Int. c1. 13031) 41/00; D03D 15/00 j ?f B k [58] Field of Search 139/11. 420 R, 420 A; Mme) e? 28/DIG. l, 1 CS, 72 CS; 264/103, 247;

225/3; 66/125 ABSTRACT A supply roll of longitudinally oriented synthetic sheet [56] References cued is provided having alternating relatively thick longitu- UNITED STATES PATENTS dinal ribs and relatively thin longitudinal webs. The 788,681 9/1969 Johnson et al. 28/1 cs Sheet is advan6dand Selected Webs are tom t0 p 2.165.986 7/1939 snow 28/72 cs a the sh et into a plurality of tapes of a desired 2,596.246 5/1952 Johnson et al. 225/] CS width. The tapes are then fed directly in line into :1 3336.645 8/1967 Mirsky l39/ll X loom or knittin machine and woven or knitted into a 3359.934 12/1967 Schwartz et al 139/420 R f b i g 3.470.594 10/1969 Kim 28/DlG. 1 3,470,685 10/1969 Hall et al. 28/DIG. 1 2 Claims, 3 Drawing Figures LOOM 0R KNITTING MACHINE US. Patent Nov. 11, 1975 3,918,135

LO0M 0R KNITTING MACHINE FIG.3

METHODS OF MAKING FABRICS FROM SYNTHETIC TAPES BACKGROUND OFTHE INVENTION .This invention relates to new and improved methods for making fabrics from synthetic tapes or ribbon monofilaments, and particularly to methods for making such fabrics by providing a synthetic sheet having lon gitudinal striationsembossed therein forming alternating relatively thick longitudinal ribs and relatively thin webs, and tearing selected'webs to separate the sheet into a plu'rality'of tapes or ribbons of a desired width and feedingthe tapes or ribbons into a loom or knitting machine for fabrication into a woven or knitted fabric.

Heretofore, in the manufacture of fabrics from synthetic tapes or ribbon monofilaments, the tapes or ribbons have been prepared by either the (l) extrusion of plastic through a die containing a series of separate slits with dimensions such that after melt drawdown, quenching and orientation the tapesor ribbons have the width desired; or (2) extrusion of plastic =through'a die which profiles or scores the film so that it can be separated into tapes or ribbons such as described, for example, in US. PanNos. 3,594,870 and 3,527,859; or (3) extrusion of plastic through a wide slit die to form a flat sheet and either before or after orientation slitting the sheet to form tapes or ribbons of the'desired width such as shown, for example, in US. Pat. Nos. 3,398,220 and3,503,106. One of the drawbacks of the first and second methods-is that complicated dies with multiple openings, ridges or profiles are'required. Furthermore, a different die is required to provide different widths of tapes or ribbons. A drawback of the third method is that'even with the use of very sharp knives or cutters to effect the slitting ofthe film, the width of the tapesis not uniform-because the film tends to follow-lines of orientation induced during melt d'rawdown or orientation after quenching. These lines of orientation may vary somewhat from the linear or machine direction over long lengths of the sheet. Thus, the ribbon monofilaments will not be uniform in strength or size. Because of the lack of uniformity in strength, frequent breaks in the tapes or ribbons during production and use are-encountered. Additionally, another is that very sharp knivesmust always be used toslit the film'without tearing, and this requires frequent replacement and sharpening of the slitting knives, necessitating shutdown of the production line. Furthermore, the knives cause nicks and notches in the edges of the slit tapes which initiate tear propagation across the tapes resulting in broken tapes. Additionally, the slitters must be initially set up with great care and precision in order'to attempt to accurately cut the film into uniform tapes.

This is time-consuming and thus costly.

Ordinarily, when a flat film is slit or otherwise separated into a plurality of tapes, the'tapes are then wound either onto a beam for use as warp yarns, or onto suitable individual packages for subsequent use. In the subsequent weaving or knitting operations, the individual packages or beams have the tapes unwound therefrom and fed into the appropriate machine to form' the woven or knitted fabric. The winding of the packages or beams and the unwinding therefrom is timeconsuming andrelatively costly. Additionally, the handling of individual packages-as 'oppose'dto handling of cient.

To overcome the-aforementioned winding'and handling problems, a slit-knit technique has been devel oped, as shown, for example, in US. Pat.- No. 3,214,943 wherein a sheet of flat film is slit directly in an in-line operation to feed a knitting machine with tapes of'a predetermined width. Similarly, a slit-weave technique is known wherein woven fabrics are made from the in-line slitting of oriented flat film. However, continuity of operation and uniformity of the knitted or woven fabrics are adversely affected by the factors previously mentioned, which result, among other things. in the need to change slitting knives frequently, line shutdowns due to tape breaks caused by te'ars which follow imperfections in the film or nicks or notches in the edges of the tapes, and imperfections in the knitted or woven fabrics due to non-uniformity of the slit tapes or ribbons.

SUMMARY OF THE INVENTION The subject invention relates to methods for making fabrics from tapes or ribbon monofilaments wherein a wide sheet of plastic film is first extruded through a die of simple construction and then'is passed through embossing rolls to emboss on either one or both sides of thefilm a pattern of continuous longitudinal striations providing alternating relatively thick longitudinal ribs and relatively thin longitudinal webs. The film is usually then longitudinally oriented. After orientation, the film can be easily and uniformly split by tearing in the web sections to provide tapes or ribbon monofilaments of desired widths. The striated film may be split in any desired web area by passing the film over such facilities as leasing rods, guide rods, comb guides with relatively dull edges or the like to effect separation of the webs withoutcutting. Any width tape or ribbon that is desired may be obtained by merely selecting which of the webs are to be torn or split. It is not necessary to use any sharp knives or rotary cutters which require frequent changing or sharpening in the subject tear method. However, the knives or cutters may be utilized in accordance with the principles 'ofthis invention by not sharpening the blades or allowing the blades to become dull so that the effect is to tear the webs with a dull edge rather than cut them. The method of this invention providesuniformityof woven or knit fabrics combined with low maintenance versatility and use of simple equipment for effecting fllmseparation or tearing into tapes or ribbons of desired widths. The longitudinally striated film is preferably t'orn into tapes in line with a knitting machine or loom. However, if desired, the film may be separated or torn into tapes which are then wound into separate packages or onto a warp beam.

Other advantages of the present invention will be apparent from the following detailed description of the invention when considered in conjunction with the following detailed drawings. It is to be noted that the drawings illustrate only typical embodiments of the invention and are therefore not to be considered limiting ofits scope, for the invention may admit to other equally effective embodiments.

BRIEF DESCRIPTION or THE DRAWINGS FIG. 1 is a perspective view illustrating a portion of a longitudinally striated sheet which can be formed into tapes or ribbons in accordance with the principles of this invention.

FIG. 2 is a view illustrating a roll of longitudinally striated sheet material and apparatus for tearing the sheet into tapes of desired width and feeding them into a loom or knitting machine in accordance with the principles of this invention.

FIG. 3 is a view illustrating an opened network having continuous longitudinal filaments and apparatus for tearing tapes of desired width from the network in accordance with the principles of this invention.

DESCRIPTION OF THE INVENTION Referring now to FIG. 1, there is shown an embossed longitudinally striated film generally designated as including a plurality of parallel continuous longitudinal ribs 11 interconnected by webs 12 of reduced thickness. The embossed sheet 10 may be prepared in a variety of different ways. A preferred method is to feed the molten plastic sheet coming from an extrusion die (not shown) into the nip of two counter-rotating rolls, one of the rolls having a ridged pattern formed therein and the other roll having either a smooth surface or also having a ridged pattern thereon. The longitudinal ribs may be formedon one side of the sheet or on both sides, or, alternatively, longitudinal main ribs may be formed on one side with transverse tie ribs formed on the other side as described in copending applications Ser. Nos. 324,028 and 324,030.

It is important that the longitudinal ribs 11 be formed parallel to the longitudinal axis of the sheet 10 so that endless tapes can be subsequently formed of uniform width. The spacing of the ribs 11 on the embossed sheet may be as few as two ribs per inch or as many as 200 ribs per inch. The thickness of the webs 12 can range from about 5 to 25% of the thickness of the ribs 11. The cross-sectional shape of the webs 12 in the sheet may be varied and be, for example, U- or V-shaped, or have other shapes. Likewise, the cross-sectional shape of the ribs 11 may be quite varied and may include, without limitation, circular, triangular, truncated or rectangular cross-sections.

The polymer during embossing of the ribs should be at a temperature considerably below the crystalline melting point in a case of a partially crystalline polymer like polypropylene, or below the softening point in the case of an amorphous polymer like polyvinyl chloride. For example, in the case of polypropylene, embossing rolltemperatures between 15C. and 130C. are quite satisfactory, while with unplasticized polyvinyl chloride, temperatures from room temperature to 50C. may be employed. The orientation by linear drawing of the embossed sheet may be effected by conventional methods for flat plastic sheets and under conditions applicable to the polymer used. A typical method is by passing the embossed sheet over a series of heated rolls rotating at progressively higher speeds. The spacing between the draw rolls is preferably kept low to minimize transverse contraction or drawdown of the sheet. The extent of orientation will depend upon the characteristics of the polymer employed and the strength and elongation properties desired. Typically, the orienta tion may vary from 2X (doubling of the length) to 10X.

An annealing or heat treating step may be included after orientation. This heat treating step, the conditions of which will depend upon the polymer employed, decreases the amount of shrinkage of the tapes or fabrics prepared from them, on exposure to elevated temperatures during use.

After orientation and annealing, the oriented longitudinally striated sheet may be wound on a supply rollfor subsequent splitting or tearing in a separate operation,

or it may be split in line and the tapes or ribbons either wound on individual packages or spools, or fed directly into a knitting machine or loom. Furthermore/if desired, the sheet may be separated into tapes prior to orientation, and the tapes may be drawn subsequently to orient them in the longitudinal direction.

Referring to FIG. 2, the forming of tapes from oriented striated sheet 10 can be readily effected with excellent uniformity by using tearing facilities such as leasing rods16, 17 and 18 or dulledge comb guides (not shown) or the like. The sheet 10 is advanced by nip rolls 19 through the lease rods which split or tear. the sheet 10 into tapes of a desired width containing two or more ribs 11. The nip rolls 19 are positioned in proximity to the lease rods and maintain tension in the sheet 10 in the longitudinaldirection uniformly across the sheet. The sheet 10 can easily be splitinto tapes of any desired width by initially cutting or tearing the leading end of the sheet 10 in the desired web areas and feeding adjacent tapes differently through the lease rods 16, 17 and 18 so that upon advancement of the sheet the lease rods direct the tapes in diverging directions and tear the sheet into tapes. For example, tape 10a containing three ribs 11 interconnected. by webs 12 is fed under lease rod 16, over lease rod 17 and under lease rod 18 while the adjacent strip 10b also having three ribs 11 per tape is fed over lease rod 16, under lease rod 17 and over lease rod 18. As strips 10a and 10b advance, the web between strips 10a and 10b is torn, thus forming uniform tapes of a desired width.

Careful alignment-of the tearing facilities is not necessary as in the case of gang slitters since the sheet will tear only in the relatively thin webs 12 between the webs 11 of the sheet. Furthermore, since the leasing rods or comb guides do not have sharp edges, there is.

no tendency for them to cut the ribs 11 as would be the case if sharp knives or rotating cutters were used.

The tearing or splitting operation previously described preferably is carried out in line with a loom or knitting machine, in which case the oriented striated sheet is unwound from a roll, passed through selected guides or lease rods for effecting splitting to the width desired, and fed into the loom at a rate coordinated with the weaving operation. An advantage of this method is that the tapes remain flat and do not twist or fold over, thus assuring maximum and uniform coverage in the woven fabric. When using individual packages of warp yarns that are fed into. the loom, it is very difficult to avoid twist, thus adversely affecting coverage and uniformity. Similarly, yarns for introduction into multiple feed knitting machines may be prepared in line with the knitting machine by unwinding the oriented striated sheet from a roll, tearing selected webs to form tapes of a desired width using suitable guides or lease rods, and feeding the tapes into the knitting machines.

If it is desired to make a more open woven or knitted fabric with greater porosity than one that can be obtained by knitting or weaving flat tapes, it is possible to first open the-embossed oriented striated film into a network structure generally designated as 20, thereby separating the main ribs into individual main filaments 21 which are interconnected by fibrils or tie ribs 22 as shown in FIG. 3. The fibrils or tie ribs 22 uniformly the hold the main filaments 21 in parallel and uniformly spaced relationship to one another.

The amount of porosity desired in the finished knit or woven fabric will determine how much the network structure is to be opened. After the sheet is opened into a network, the desired tape width is selected and the fibrils in the areas between adjacent tapes are split or torn by the lease rods 23, 24 and 25 or other facilities as previously described. The network structures may be formed by any method, such as, for example, by mechanical fibrillation as described in US. Pat. No. 3,495,752 or by spontaneous fibrillation of sheets embossed on two sides which is described in the aforementioned US. patent applications Ser, Nos. 324,028 and 324,030. The two-side embossing methods described in the aforementioned patent applications may be particularly desirable for use in making open tapes for fabrics because the tie filaments on the opposite side of the sheet provide dimensional stability as well as strength. In the two-side embossing method, the sheet is embossed on one side to form a plurality of parallel main ribs in the longitudinal direction and on the opposite side to form a plurality of parallel tie ribs in a direction transverse to that of the main ribs. Preferably, the ratio of the cross-sectional area of the main ribs to the tie ribs is at least 1.5 to 1, and the ratio of the height of the main ribs to the thickness of the webs between the main ribs is at least 3 to 1. Alternatively, the tie ribs can be formed in a discontinuous manner so that no substantial portion crosses over the opposite side of the main ribs. The direction of the tie ribs on the reverse side of the sheet should be transverse to that of the main ribs, but need not be perpendicular to it. Typically, any angle between 45 and 90 from the longitudinal direction of the main ribs is satisfactory. If two-side embossing is employed, the tapes produced are stiffer, i.e., more resistant to curling or overlapping, because of the presence of the tie filaments interconnecting the main filaments as illustrated in FIG. 3.

Conjugate or bicomponent plastic sheets may also be employed wherein two or more different polymers are extruded together to form sheets containing layers of separate polymers. One layer of the sheet typically has a component made of a relatively high melting point polymer with the remaining portion being made of a lower melting point polymer. A fabric made from such tapes can be easily bonded at the cross-over points by hot calendering or at intermittent points by use of hot embossed pressure rolls positioned at selected points. Such bonding can eliminate raveling and improve the dimensional stability of fabrics.

The subject methods are applicable to thermoplastic fiber-forming polymers generally. These include polyolefins such as low density polyethylene, high density polyethylene, polypropylene homopolymer, propylene random copolymer. propylene random copolymers containing up to 10% of another olefin. block copolymers of propylene containing up to 25% of another olefin, polyamides such as nylon 6, nylon 66, polyesters such as polyethylene terephthalate and other high molecular weight thermoplastic polyesters, and polyvinyl chloride. Conjugate plastic sheets as described above are also applicable. Additionally, bicomponent plastic sheets in which a higher melting component is used to form the major portion of the main rib may be employed. Furthermore, alloys. and mixtures of polymers may also be employed.

What I claim and desire to protest by Letters Patent l. A method of making fabrics comprising:

providing a supply roll of a longitudinally oriented synthetic sheet having longitudinal striations embossed therein forming alternating relatively thick longitudinal ribs and relatively thin longitudinal webs;

advancing said sheet from said supply roll;

initially separating a portion of said sheet into a plurality of tapes of a desired width;

advancing adjacent tapes in diverging directions vertically away from each other while maintaining tension in the longitudinal direction uniformly across said sheet to tear the webs between said adjacent tapes; and

continuously feeding said tapes into a fabrication machine to form a fabric therefrom.

2. A method of making fabrics comprising:

providing a supply roll of a longitudinally oriented open network structure having a plurality of parallel spaced continuous longitudinal filaments interconnected in the spaces between adjacent filaments by fibrils;

advancing said sheet from said supply roll;

initially separating a portion of said network structure into a plurality of tapes of a desired width; advancing adjacent tapes in diverging directions vertically away from each other while maintaining tension in the longitudinal direction uniformly across said network structure to tear the fibrils between said adjacent open network tapes; and continuously feeding said open network tapes into a fabrication machine to form a fabric therefrom. 

1. A method of making fabrics comprising: providing a supply roll of a longitudinally oriented synthetic sheet having longitudinal striations embossed therein forming alternating relatively thick longitudinal ribs and relatively thin longitudinal webs; advancing said sheet from said supply roll; initially separating a portion of said sheet into a plurality of tapes of a desired width; advancing adjacent tapes in diverging directions vertically away from each other while maintaining tension in the longitudinal direction uniformly across said sheet to tear the webs between said adjacent tapes; and continuously feeding said tapes into a fabrication machine to form a fabric therefrom.
 2. A method of making fabrics comprising: providing a supply roll of a longitudinally oriented open network structure having a plurality of pArallel spaced continuous longitudinal filaments interconnected in the spaces between adjacent filaments by fibrils; advancing said sheet from said supply roll; initially separating a portion of said network structure into a plurality of tapes of a desired width; advancing adjacent tapes in diverging directions vertically away from each other while maintaining tension in the longitudinal direction uniformly across said network structure to tear the fibrils between said adjacent open network tapes; and continuously feeding said open network tapes into a fabrication machine to form a fabric therefrom. 